Final characterization by mass spectroscopy, NMR, and light spectroscopy of two adenine derivates formed by reaction with Beta-propiolactone is being done. Conditions for maximum yield of these compounds in DNA are being defined and a search for a repair enzyme which recognizes these derivatives start. Purification of an N-glycosylase which recognizes 3-methyladenine from E. coli and from rat liver continues. A study of in vivo repair of MNU treated murine lymphoma L-2178Y cells, both radiosensitive and radioresistant has started.